Reference to an int type, whereas it's a Py_ssize_t as the synopsis states.

Doc/c-api/arg.rst

@@ -262,9 +262,9 @@ of the C variable(s) whose address should be passed.
 ``w#`` (read-write character buffer) [char \*, Py_ssize_t]
    Like ``s#``, but accepts any object which implements the read-write buffer
    interface.  The :ctype:`char \*` variable is set to point to the first byte
-   of the buffer, and the :ctype:`int` is set to the length of the buffer.
-   Only single-segment buffer objects are accepted; :exc:`TypeError` is raised
-   for all others.
+   of the buffer, and the :ctype:`Py_ssize_t` is set to the length of the
+   buffer.  Only single-segment buffer objects are accepted; :exc:`TypeError`
+   is raised for all others.
 
 ``w*`` (read-write byte-oriented buffer) [Py_buffer \*]
    This is to ``w`` what ``s*`` is to ``s``.